Crohn's disease (CD) is a form of inflammatory bowel disease (IBD) characterized by chronic transmural inflammation and skip lesions that can involve any segment of the gastrointestinal tract. The prevalence of CD has been increasing in recent years. An early accurate detection, determination of prognosis, as well as predicting appropriate therapy are therefore important to curb such increased prevalence.
The pathophysiology of CD is likely related to genetic, environmental and immune system factors. With regard to the immune system, there is evidence to suggest that an overactive intestinal mucosal immune system may be driven at least in part by a reaction to normal/altered luminal flora and autoantigens (AAgs). One manifestation of such a dysregulated immune response is the presence of CD-specific antibodies against gut microorganisms and AAgs. These include antibodies against microbial antigens (e.g., Flagellin, I2, Saccharomyces cerevisiae (ASCA)) and autoantibodies (AAbs) such as anti-neutrophil cytoplasmic antibodies (ANCA) and pancreatic antibodies (PAb). To date, the presence of specific antibodies in the serum of patients with CD may help in detection, prognosis, and predicting response to therapy. However, most clinically used serological antibodies were discovered years ago and have a limitation by frequent false positives and an inability to accurately predict disease course. Therefore, there is a need for better diagnostic and prognostic CD markers.
Early studies on AAbs in CD patients used immunofluorescence or whole cell ELISA assays on neutrophils, pancreas, goblet cells and colonic epithelial cells probed with patient sera. Early studies on AAbs in CD patients used immunofluorescence or whole cell ELISA assays on neutrophils, pancreas, goblet cells and colonic epithelial cells probed with patient sera. Although whole-cell signals have been observed in CD for decades, the antigens recognized by these immunofluorescence assays remain largely unknown. This approach has proven to be ineffective, only two AAb targets of PAb have been discovered through mass spectrometry identification of reactive western blot spots. Challenges associated with methods that involve western blot include low throughput, inadequate quantification, and poor reproducibility. While all these technical challenges can be overcome, the level of effort needed to thoroughly analyze even a single sample prevents this approach from use in large clinical sample sets.
Progress in identifying individual autoantigens and autoantibodies in Crohn's disease has been challenging due to limitations of available immunoassays.